A typical “flying probe” test apparatus operates electromechanically, under software control, to test a plurality of predetermined points on a printed circuit board. The printed circuit board to be tested is mounted in the test apparatus in a fixed position, and the probe is then moved automatically to test user-selected points on the board. The flying probe assembly, typically with a single probe, is used to test the electrical characteristics of a particular circuit portion on the board by supplying a test signal to the selected points and then receiving the return signal from the circuit. Typically, a single pin probe will require an electrical signal reference or return path connection, which could be a ground wire externally connected to the circuit. However, the ground return path could also adversely affect the test measurement and produce inaccurate results.
In RF (radio frequency) measurements, the ground return path is important to the test. Calibration procedures are required to take into account the spacing and the particular dielectric material between the transmission line and the ground line return path. The spacing between the transmission line and the ground line could vary in length and orientation and produce differences in test results.
Most prior art probe assemblies have a fixed physical spacing between the test pin and the ground pin, although some are mechanically adjustable so that the same probe can be used for different pin-to-ground spacings and orientations. Generally, the use of specific materials and short ground wires are important to minimize the losses and the degeneration of the test signal.
In addition, some prior art probe assemblies include two probes, so that the same probe assembly can be used for different pin-to-ground spacings and orientations, as well as different pin-to-pin connections and tests. The two probes can be separately adjustable, typically mechanically, to allow for different spacings and orientations of the two probes. However, such dual probe arrangements are typically quite complex, expensive and difficult to implement.
Hence, there is a specific need for a low-cost flying probe assembly in which two probes can be moved in such a manner to produce variable spacings and orientations, for cost-effective access to a plurality of test points on an electronic circuit.